This invention relates to a plated metal wire having enhanced corrosion resistance required of metal materials for outdoor and exposed uses such as construction, revetments, fishing nets, fences, etc., and a method and an apparatus to produce the plated metal wire. The plated metal wires include: plated steel wires such as steel wires for wire mesh, bridge cables, PWS wires, PC wires, ropes and the like; plated steel wires for machine components such as screws, bolts, springs and the like; and other steel products.
Among plated metal wires, and among plated steel wires in particular, galvanized steel wires and zinc-aluminum alloy plated steel wires, which are superior to the galvanized steel wires in corrosion resistance, are commonly used. The zinc-aluminum alloy plated steel wires are produced, generally, by subjecting a steel wire to the following sequential processes: washing, degreasing, or other means of cleaning; flux treatment; plating either by a two-step plating process composed of a first step of hot dip plating in a plating bath mainly containing zinc and a second step of hot dip plating in a Znxe2x80x94Al alloy bath containing 10% of Al or by a one-step plating process in a Znxe2x80x94Al alloy bath containing 10% of Al; then, after vertically extracting the wires from the plating bath, cooling; and winding into coils.
Although the zinc-aluminum alloy plated steel wire has a good corrosion resistance, the wire surface is made smooth by the action of the surface tension during the wire extraction. Therefore, when the wire is formed into a structure such as wire mesh, a fastening wire, etc., the structure does not have a sufficiently roughened surface or a irregular surface. For this reason, there is a problem that the structure slips easily when laid on the ground.
Another problem is that, when the plated steel wire is further coated with resin, for example, the adhesion of resin is poor owing to the smooth surface.
To cope with these problems, methods were studied to make the wire surface rougher. An example of such an attempt is a technique applied to galvanized steel sheets used for scaffolds for building construction work, molding forms for concrete casting work and the like proposed in Japanese Unexamined Patent Publication No. H9-78216, wherein a plated surface is roughened after hot dip galvanizing by blowing water droplets 20 to 300 xcexcm in size at a water density of 50 to 750 cc/m2. An evenly distributed surface roughness is formed by this method, but the method is meant for steel sheets, and there is a problem that it is inapplicable to a steel wire because, when applied to a steel wire without modification, an even distribution of the roughness in the circumference direction is not secured. Another problem with the method is that the roughened surface are small owing to the small amount of water and a sufficient friction is not obtained.
In view of the above problems, the object of the present invention is to provide a plated metal wire with high friction for outdoor and exposed uses, such as gauze for constructions, net cages for revetments, fishing nets, outdoor fences, etc., and a method and an apparatus to produce the plated metal wire.
The gist of the present invention, which solves the above problems, is as follows:
(1) A plated metal wire characterized in that; the region where at least 3 projections, each 3 xcexcm or more in height, per 1 mm along its circumference exist occupies 10% or more of the circumference, and the circumference having the projections thus distributed occupies 10% or more of any given portion along the length of the metal wire.
(2) A plated metal wire characterized in that the region where the surface roughness (Ra) of the plated metal wire is 2.5 xcexcm or more occupies 10% or more of its circumference and 10% or more of any given portion along the length of the metal wire.
(3) A plated metal wire according to the item (1) or (2), characterized in that the plating is hot dip plating of aluminum, aluminum alloy, tin, tin alloy, zinc or zinc alloy.
(4) A plated metal wire according to the item (1) or (2), characterized in that the plating is electroplating of nickel, copper, copper alloy, aluminum, aluminum alloy, zinc or zinc alloy.
(5) A plated metal wire according to any one of the items (1) to (4), characterized in that the core metal wire consists of a steel containing, in mass, 0.02 to 1.15% of C, 1% or less of Si and 1% or less of Mn
(6) A plated metal wire according to the item (5), characterized in that the core metal wire consists of a steel containing, in mass, 0.02 to 0.25% of C, 1% or less of Si and 0.6% or less of Mn.
(7) A method to produce a plated metal wire characterized in that, on the plated surface, the region where at least 3 projections, each 3 xcexcm or more in height, per 1 mm along its circumference exist occupies 10% or more of a circumference, and the circumference having the projections thus distributed occupies 10% or more of any given portion along the length of the metal wire, as a result of applying hot dip plating of aluminum, aluminum alloy, tin, tin alloy, zinc or zinc alloy to the core metal wire consisting of a steel wire containing, in mass, 0.02 to 1.15% of C, 1% or less of Si and 1% or less of Mn and then cooling the plated metal wire by blowing an atomized cooling medium.
(8) A method to produce a plated metal wire according to the item (7), characterized in that, on the plated surface, the region where the surface roughness (Ra) of the plated metal wire is 2.5 xcexcm or more occupies 10% or more of its circumference and 10% or more of any given portion along the length of the metal wire.
(9) An apparatus to produce a plated metal wire by immersing a metal wire or a pre-plated metal wire in a hot dip plating pot, characterized by having:
a purging device to prevent a plating bath surface and the plated metal wire surface from oxidizing, installed at the position where the metal wire is extracted from the hot dip plating pot;
a temperature controller to control the surface temperature of the plated metal wire to a prescribed temperature; and
a cooler to blow a cooling medium onto the surface of the plated metal wire controlled to the prescribed temperature for the purpose of forming roughness on its surface.
(10) An apparatus to produce a plated metal wire according to the item (9), characterized in that two or more nozzles to blow the cooling medium are arranged in the cooler at equal intervals in the circumferencial direction of the metal wire.
(11) An apparatus to produce a plated metal wire according to the item (9), characterized in that the distance between each of the nozzles to blow the cooling medium in the cooler and the plated metal wire is 10 to 500 mm.